The Vampire Unleashed by Tricia Barr

Immortality is no fairy tale.
Crimson Wilkinson may have narrowly escaped destruction at the hands of Delilah, but the cost of that escape proves to be a hefty one. As the first Amarant vampire in centuries, she is struggling with controlling both her demanding thirst and her insurmountable new powers. If that weren’t enough, the Salem coven is without a leader, and Crimson owes them greatly. If she does not step up as their new leader, they may join her growing enemies and crush her. The stress of it all begins to go to her head, and she fears she is losing her mind.
But that’s not the only threat darkening her world. Vampires are dying of mysterious causes. Crimson may have to face losing everything and everyone she holds dear, including Nicholae.
So much for happily ever after…